Thermoplastic resin compositions resistant to fluorinated/chlorinated hydrocarbons and the use thereof

ABSTRACT

A high nitrile thermoplastic resin composition having fluorinated/chlorinated hydrocarbon resistance and comprising a specifically defined graft copolymer obtained by polymerizing a vinyl cyanide compound and an aromatic vinyl compound in the presence of a conjugated diene-based synthetic rubber, or a blend of it and a vinyl cyanide compound/aromatic vinyl compound copolymer, and its use as a fluorinated/chlorinated hydrocarbon-resistant internal box of a refrigerator.

TECHNICAL FIELD

The present invention relates to an internal box of a refrigerator whichhas excellent flon resistance. More specifically, the present inventionrelates to an internal box of a refrigerator which is endowed withanti-flon property such as high stress cracking resistance, particularlyagainst HCFC-123 and HCFC-141b, by using a high nitrile contentthermoplastic resin having a specific composition. The term "flon" isused in the same meaning as a fluorinated/chlorinated hydrocarbon.

In addition, the phraseology "an internal box of a refrigerator"includes the interior of a door of the refrigerator.

BACKGROUND ART

The housing of a refrigerator recently used is one formed as a thermalinsulation housing manufactured by a method wherein a space between aninternal box and an external box which has been constructed by combiningthe two boxes is filled with a foam produced by injecting, foaming andsolidifying a rigid polyurethane foam stock within the space (referredto hereinafter as in-situ foaming method). Also in the door of therefrigerator, a rigid polyurethane foam is charged as a thermalinsulator by the in-situ method between the space which has beenconstructed by combining the internal and external boxes.

Hitherto, an ABS resin widely used for various purposes has beenprimarily used as the internal box of a refrigerator. The phraseology"ABS resin widely used for various purposes" means a resin compositionwhich is obtained polymerizing a monomer mixture of 10-40% by weight ofa of a vinyl cyanide compound and 60-90% of an aromatic vinyl compoundin the presence poly(conjugated diene) synthetic rubber or, in otherwords, by graft copolymerizing the monomer mixture; or a resincomposition in which a copolymer of a vinyl cyanide compound/aromaticvinyl compound is blended with the graft copolymer so that the contentof the vinyl cyanide compound is in the range of 10-40% by weight.

As the reason why an ABS resin has been used as a material of aninternal box of a refrigerator, there are mentioned a high balance ofphysical properties such as rigidity and impact property, easyformability, excellent glossy appearance and stress cracking resistanceagainst a flon such as CFC-11 (trichloromonofluoromethane) which is afoaming agent for a rigid polyurethane foam. The internal box of arefrigerator is produced by a heat forming method of a thermoplasticresin sheet, for example by a vacuum forming technique, so that thesheet should have easy formability, particularly vacuum formability. Theinternal box obtained by the vacuum forming has an average thickness ofless than 1 mm, and thus it should have high modulus in order to avoiddeformation. If a rigid polyurethane foam is charged into a space whichis formed by combining an internal box made of the ABS resin with anexternal box made of a steel sheet by the in-situ method, the rigidpolyurethane foam adheres to the ABS resin and the steel sheets thuscausing stress attributed to the difference in the linear expansioncoefficients of the steel sheet/rigid polyurethane foam/ABS resin duringthe operation of the refrigerator. Therefore, the internal box shouldhave stress cracking resistance against CFC-11 as a foaming agent forthe rigid polyurethane foam. As notch effect is produced by the adhesionof the rigid polyurethane foam, the internal box is required to have ahigh notched Izod impact value. Furthermore, excellent gloss is requiredin order to improve the appearance of the refrigerator.

CFC-11 as a foaming agent for a rigid polyurethane foam containschlorine and is non-decomposable. Thus, it is suspected that it candestroy the ozone stratum in the stratosphere and there is thus aworldwide trend to the restriction of its use. As an alternative toCFC-11 for use as a foaming agent for a rigid polyurethane foam, anotherfluorinated/chlorinated hydrocarbon such as HCFC-123(1-hydro-1,1-dichloro-2,2,2-trifluoroethane) is now to be used. However,HCFC-123 has by far a higher solubility of an ABS resin therein thanCFC-11, and the internal box of a refrigerator made of the ABS resin inwhich a rigid polyurethane foam has been charged by the in-situ methodwill easily produce craze or crack under stress to lose the articlevalue of the refrigerator. Therefore, under such a trend, it isnecessary to prepare an internal box of a refrigerator and the interiorof a refrigerator door with a material which has a stress crackingresistance against HCFC-123, and in the same time as usual has a highbalance of physical properties such as rigidity and impact property,easy formability and excellent glossy appearance.

DISCLOSURE OF THE INVENTION

The present inventors have conducted earnest researches. As a result,they have discovered that a high nitrile content thermoplastic resinhaving a specific composition has a stress cracking resistance againstHCFC-123 as well as a high balance of physical properties such asrigidity and impact property, easy formability and excellent appearance,and that an internal box of a refrigerator which has overcome theaforementioned problems is obtained by using the high nitrile contentthermoplastic resin. Thus, the present invention has been accomplished.

In other words, the flon-resistant internal box of a refrigeratoraccording to the present invention is manufactured with a thermoplasticresin composition, which thermoplastic resin composition comprises (a) ahigh nitrile thermoplastic resin composition comprising a graftcopolymer which is obtained by polymerizing, in the presence of 10 to 20parts by weight of a conjugated diene-based synthetic rubber, 80 to 90parts by weight of a monomer mixture consisting essentially of 50 to 75%by weight of a vinyl cyanide compound and 25 to 50% by weight of anaromatic vinyl compound, the parts by weight and % by weight beingrespectively the values based on the total of the above-describedcomponents in question being 100, and/or (b) a high nitrilethermoplastic resin composition comprising a blend of a graft copolymerwhich is obtained by polymerizing, in the presence of 20 to 70 parts byweight of a conjugated diene-based synthetic rubber, 30 to 80 parts byweight of a monomer mixture consisting essentially of 50 to 75% byweight of a vinyl cyanide compound and 25 to 50% by weight of anaromatic vinyl compound, and a vinyl cyanide compound/aromatic vinylcompound copolymer having a content of the vinyl cyanide compound of 50to 75% by weight, wherein the resin composition has a rubber content of10 to 20% by weight, the parts by weight and % by weight beingrespectively the values based on the total of the above-describedcomponents in question being 100.

The high nitrile content thermoplastic resin composition used as aninternal box material of a refrigerator has a high stress crackingresistance against flons such as CFC-11, HCFC-123, HCFC-141b andmixtures thereof used as a foaming agent. The high nitrile contentthermoplastic resin composition in accordance with the present inventionfalls within a class of ABS resins and thus has properties which areinherent in the ABS resins and are required for the internal box of arefrigerator.

The resin composition according to the present invention has thefollowing excellent properties.

i) Vacuum formability

The specific viscosity of a matrix portion of the resin composition isadjusted to be at a preferable level, and thus the vacuum-formedinternal box of a refrigerator is uniform and improved.

(ii) Punching property

The internal box of a refrigerator manufactured from the resincomposition of the present invention has excellent rigidity and impactresistance and thus scarcely produces undesirable phenomena such as thegeneration of cracking from holes produced upon punching.

(iii) Adhesiveness to polyurethane foam

The intrernal box of a refrigerator manufactured from the resincomposition of the present invention, which has a moderate vinyl cyanidecontent, thus has a good adhesiveness to polyurethane foam. If theinternal box has a higher vinyl cyanide content in the resin compositionused than the range defined by the present invention, it may be lessadhesive to the foam and may thus be difficult to use successfully as aninternal box of a refrigerator. If the internal box has a lower vinylcyanide content in the resin composition used than the range defined bythe present invention, it may be less resistant to flons and may thuscause stress cracking at the portion of the internal box of arefrigerator, where distortion is concentrated.

Therefore, the present invention is expected to have an extensiveutility in the field of producing an internal box of a refrigeratorunder the trend where use of flons is restricted.

BEST MODE FOR THE PRACTICE OF THE INVENTION Thermoplastic resincomposition (part 1)

The thermoplastic resin composition for use as an internal box materialof a refrigerator according to the present invention comprises a graftcopolymer comprising a synthetic rubber based on a conjugated diene asthe so-called "trunk polymer" of the graft copolymer, and thethermoplastic resin compositions according to the present invention arebasically classified into the following two types in view of the methodsfor providing the resin composition with a prescribed rubber content anda high nitrile content:

(a) those directly obtained as a thermoplastic resin composition havinga conjugated diene-based synthetic rubber content in the range of 10 to20% by weight produced by polymerizing 80 to 90 parts by weight of avinyl cyanide compound (referred to herein as A)+an aromatic vinylcompound (referred to herein as S) (A: 50 to 75% by weight; S: 25 to 50%by weight) in the presence of 10 to 20 parts by weight of a conjugateddiene-based synthetic rubber (referred to herein as B) to form a graftcopolymer. The terms "parts by weight" and "% by weight" used herein andhereinafter are the values based on the total of the components inquestion as 100; and

(b) those produced as a blend of a thermoplastic resin compositionhaving a prescribed rubber content by incorporating a high rubber/highnitrile ABS resin with a high nitrile AS resin, wherein a graftcopolymer produced by polymerizing 30 to 80 parts by weight of a vinylcyanide compound+an aromatic vinyl compound (A: 50 to 75% by weight; S:25 to 50% by weight) in the presence of 20 to 70 parts by weight of theconjugated diene-based synthetic rubber is blended with a vinyl cyanidecompound aromatic vinyl compound copolymer (A content: 50 to 75% byweight).

According to the present invention, the composition (b) is preferredbecause of its higher degree of freedom or flexibility in thecombination between material composition and physical propertiesobtainable. The compositions (a) and (b) can be used as an admixturethereof.

In passing, the graft copolymerization comprises polymerizing, in thepresence of a trunk polymer, a monomer which should give a polymer toform a branch to the trunk, and it may thus be inevitable even in thecase of (a), that a vinyl cyanide compound-aromatic vinyl compoundcopolymer is produced which is not bonded as a branch to the trunk.

Conjugated diene-based synthetic rubber

It is a conjugated diene-based synthetic rubber used as "the trunkpolymer" of a graft copolymer that provides a thermoplastic resincomposition used in the present invention with impact resistancerequired for an internal box material of a refrigerator.

The conjugated diene-based synthetic rubber means either one of ahomopolymer of a conjugated diene, a copolymer of conjugated dienes or arandom or a block copolymer of a conjugated diene with anothercomonomer, at least a major portion of rubber elasticity of which isattributable to the conjugated diene.

Examples of the conjugated diene-based synthetic rubber include, forexample, polybutadiene, polyisoprene, polychloroprene, abutadiene-styrene copolymer, a butadiene-acrylonitrile copolymer, andthe like. Preferably, polybutadiene, butadiene-styrene copolymers andbutadiene-acrylonitrile copolymers are used. These conjugateddiene-based synthetic rubbers can be used in combination.

The conjugated diene-based synthetic rubber is utilized in connectionconcern with the thermoplastic resin composition of the presentinvention to produce a graft copolymer having the rubber as a trunkpolymer, and this graft copolymer is generally produced by emulsionpolymerization of a certain monomer in a latex of the conjugateddiene-based synthetic rubber. The latex of the conjugated diene-basedsynthetic rubber has preferably an average particle diameter of therubber particles in the range of 0.01 to 10 μm, particularly in therange of 0.1 to 0.5 μm. If a synthetic rubber latex having an averageparticle diameter in the latter range is used, excellent balance ofphysical properties can be attained.

Monomers

A vinyl cyanide compound is one of the monomers which should form abranch polymer.

The vinyl cyanide compound used according to the present invention meansacrylonitrile, methacrylonitrile or the like, among which acrylonitrileis preferably used. These vinyl cyanide compounds can be used incombination.

An aromatic vinyl compound as another monomer which should form a branchpolymer includes styrene, nucleus- and/or side chain-substitutedstyrenes such as α-methylstyrene, p-methylstyrene, vinyltoluene and thelike, among which styrene is preferably used. These aromatic vinylcompounds can be used in combination.

It is necessary for the total of the monomer mixture used for the graftcopolymer according to the present invention to comprise 50-75% byweight, preferably 50-66% by weight, of a vinyl cyanide compound and25-50% by weight, preferably 34-50% by weight, of an aromatic vinylcompound. If the content of the vinyl cyanide compound is less than 50%by weight, stress cracking resistance against HCFC-123 may beinsufficient. On the other hand, if the vinyl cyanide compound exceeds75% by weight, easiness of formability may be lost.

The monomer which should form a branch polymer in the present inventioncan contain a small amount of another copolymerizable comonomer inaddition to the abovementioned two components. This is the reason whythe monomer is defined as "consisting essentially of a vinyl cyanidecompound and an aromatic vinyl compound." As the specific examples ofsuch comonomers, there are mentioned esters of acrylic acid ormethacrylic acid (e.g. C₁ -C₆ alkyl esters such as methyl, ethyl,cyclohexyl esters), vinyl esters (e.g. vinyl acetate), and the like.

Preparation of a graft copolymer

The graft copolymer according to the present invention is generallyprepared by emulsion polymerization. Molecular weight modifiers,initiators and emulsifiers which are usually used in emulsionpolymerization can be used. For example, mercaptans are used as themolecular weight modifiers, organic peroxides or persulfates are used asthe initiators, and fatty acid salts, alkyl sulfate salts, alkylbenzenesulfonic acid salts, or alkyl diphenyl ether disulfonic acid salts areused as the emulsifiers.

Preferred graft polymerization is as follows: Prescribed amounts of aconjugated diene-based synthetic rubber, an emulsifier, an initiator andwater are charged in a polymerization vessel and agitated under anitrogen stream. The monomer mixture is divided into two batches, whichare used in two stages. At a predetermined temperature, 90-98% by weightof a first batch of monomer (mixture) (the total of this monomer and asecond batch of monomer described below being 100% by weight),comprising 51-84% by weight of a vinyl cyanide compound and 16-49% byweight of an aromatic vinyl compound and a predetermined amount of amolecular weight modifier are continuously added within a predeterminedperiod of time to effect graft copolymerization. After the addition ofthe first stage monomer mixture, 2-10% by weight of a second stage orremaining batch of monomer comprising an aromatic vinyl compound (thetotal of this monomer and the aforementioned first batch of monomer(mixture) being 100% by weight) is continuously added within apredetermined period of time at a predetermined temperature to completethe graft copolymerization. In this connection, along with the progressof the graft copolymerization, a predetermined amount of the initiatorand a predetermined amount of water can be continuously added within aprescribed period of time. Such a polymerization method wherein thecomposition of the monomer mixture to be added continuously during thegraft copolymerization is varied is desirable for keeping the stabilityof the high nitrile content resin latex during and after polymerizationat a higher level. The addition of the first stage monomer mixture isconducted preferably in 2 hours or more in order to make the compositionof the graft copolymer produced uniform. The addition of the secondstage monomer is conducted preferably in 20 minutes or more in order tostabilize the high nitrile content resin latex effectively duringpolymerization. The amounts of an emulsifier, an initiator and amolecular weight modifier and the temperature for performing the graftcopolymerization are varied depending on the target values for thedegree of grafting or the molecular weight of a graft copolymerproduced. The graft copolymer produced is obtained in a conventionalmanner in an emulsion polymerization method including coagulation ofemulsion, washing and drying of the coagulum.

Degree of grafting and other parameters

The graft copolymer according to the present invention preferably meetsthe following conditions.

0.30≦(G-R)/R≦0.50, preferably

0.37≦(G-R)/R≦0.50

wherein

G: a percentage by weight of a gel in the graft copolymer, calculated onthe insoluble matter obtained by dissolution of the graft copolymer inacetonitrile and then separation from the solution by centrifugation.

R: a rubber content of the graft copolymer.

If the value of (G-R)/R (referred to hereinafter as degree of grafting)is less than 0.30, a high physical property balance of rigidity andimpact resistance may tend to be decreased. On the other hand, if thedegree of grafting exceeds 0.50, easiness of formability may tend to bedecreased.

The molecular weight of the graft copolymer according to the presentinvention is preferably such that the specific viscosity, which isdetermined on a solution of 0.1 g of an acetonitrile soluble portion ofthe graft copolymer in 100 ml of dimethylformamide measured by aviscometer, is in the range of 0.04-0.09, more preferably 0.058-0.085for attaining easy formability.

AS resins

According to the present invention, the vinyl cyanide compound/aromaticvinyl compound copolymer to be blended with a graft copolymer when thegraft copolymer has a high rubber content/high nitrile content, shouldcomprise 50-75% by weight, preferably 50-66% by weight, of a vinylcyanide compound and 25-50% by weight, preferably 34-50% by weight, ofan aromatic vinyl compound. If the content of the vinyl cyanide compoundis less than 50% by weight, stress cracking resistance against HCFC-123may be insufficient. On the other hand, if the content of the vinylcyanide compound exceeds 75% by weight, easiness of formability may belost.

The vinyl cyanide compound/aromatic vinyl compound copolymer, or ASresin, is generally produced by the suspension polymerization method.Molecular weight modifiers, initiators, suspension stabilizers andsuspension stabilizing aids which are usually used in suspensionpolymerization can be used. For example, mercaptans and terpenes areused as the molecular weight modifiers, azo compounds are used as theinitiator, polyvinyl alcohol or acrylic acid copolymers are used as thesuspension stabilizers, and salts are used as the suspension stabilizingaids. The polymerization method is also conducted according to the oneusually used in the suspension polymerization method. Predeterminedamounts of a monomer mixture, a molecular weight modifier, a suspensionstabilizer, a suspension stabilizing aid and water are charged in apolymerization vessel, and an initiator is injected with agitation undera nitrogen stream to start copolymerization. Immediately after theinitiation, the monomers are successively added so that the compositionof the monomer mixture in the polymerization vessel will be at a desiredlevel to complete the copolymerization. The composition of the monomermixture and the amounts of the molecular weight modifier, the suspensionstabilizer and the suspension stabilizing aid may vary depending on thetarget values for the component ratios and the molecular weights of thevinyl cyanide compound/aromatic vinyl compound copolymer produced. Thevinyl cyanide compound/aromatic vinyl compound copolymer produced issubjected to removal of unreacted monomers, and washed and dried by ausual method in the suspension polymerization method.

The molecular weight of the vinyl cyanide compound/aromatic vinylcompound copolymer according to the present invention is preferably suchthat its specific viscosity is in the range of 0.04-0.09, morepreferably 0.058-0.085, for attaining easy formability.

The descriptions for the vinyl cyanide compound and the aromatic vinylcompound and for "the monomer mixture consisting essentially of thesemonomers" will apply to the AS resins.

Rubber contents and other parameters

It is required for the high nitrile thermoplastic resin compositionaccording to the present invention to have a rubber content in the rangeof 10-20% by weight, preferably 13-18% by weight, in order to obtainphysical properties suitable to the internal box of a refrigerator. Ifthe rubber content is less than 10% by weight, impact resistance may beinsufficient and cracking may thus be generated when an article housedwithin the refrigerator hits against it. On the other hand, if therubber content exceeds 20% by weight, rigidity may be insufficient and avacuum-formed internal box is deformed. As described above, in orderthat the rubber content of the high nitrile thermoplastic resincomposition may be in the range of 10-20% by weight, a graft copolymerhaving a rubber content of 10-20% by weight may be directly used, or thevinyl cyanide compound/aromatic vinyl compound copolymer may be blendedwith a graft copolymer having a rubber content of 20-70% by weight sothat the rubber content in the blend will be 10-20% by weight. When thegraft copolymer and the vinyl cyanide compound/aromatic vinyl compoundcopolymer are blended, the ratio of the vinyl cyanide compound/aromaticvinyl compound in the graft copolymer and the ratio of the vinyl cyanidecompound/aromatic vinyl compound in the vinyl cyanide compound/aromaticvinyl compound copolymer desirably have a difference not exceeding 10%by weight. If the difference is large, uniformity of the blend may belowered and thus a high physical property balance may not be obtained.On the other hand, if the molecular weight of the graft copolymer andthe molecular weight of the vinyl cyanide compound/aromatic vinylcompound copolymer lie respectively in the above-mentioned ranges, theymay be in any combinations provided that target physical properties andformability are obtainable in the blend.

The specific viscosity of the high nitrile thermoplastic resincomposition, or more precisely the specific viscosity of theacetonitrile-soluble portion of the composition, is preferably in," therange of 0.04-0.09, more preferably 0.058-0.085. A specific viscosityless than 0.04 may produce unfavorable results such as poor vacuumformability as the internal box of a refrigerator, and a specificviscosity exceeding 0.09 may produce unfavorable results such as poorcompatibility of the graft copolymer in the resin composition, poorformability or the heat decomposition or scorching of the composition.

Formation of a composition

The thermoplastic composition as the object of the present invention canbe produced by any means which is capable of uniformly kneading thepredetermined components, preferably means which result in softening ormelting of resin components.

In mixing, conventional mixing apparatuses in the melt mixing of resinssuch as a uniaxial extruder, a biaxial extruder, a Banbury mixer or akneader can be used.

In this connection, additives such as an anti-oxidant, a UV absorber, alubricating agent or an antistatic agent, or a coloring matter can beincorporated.

Formation of the internal box of a refrigerator

The high nitrile thermoplastic resin composition according to thepresent invention is formed into an internal box or a door interior of arefrigerator by a conventional manner for producing an internal box of arefrigerator. Generally, a resin composition is melted, formed into asheet or plate and chilled and solidified with a roll by means of anextruder provided with a coat hanger die. Subsequently, the sheet isformed into an interior and a door internal box of a refrigerator by avacuum molding machine.

Thermoplastic resin composition (part 2)

The resin compositions for a refrigerator according to the presentinvention are the ones described above including its production methodand the formation of the composition. The preferred one among them hasalso been described above.

In other words, the preferred resin composition for a refrigeratoraccording to the present invention is characterized by the followingconditions (i)-(iv).

(i) The high nitrile thermoplastic resin composition is a blend of:

(A) a graft copolymer obtained by polymerizing 30-80 parts by weight,preferably 40-70 parts by weight, of a monomer mixture consistingessentially of 50-75% by weight, preferably 50-66% by weight, of a vinylcyanide compound and 25-50% by weight, preferably 34-50% by weight, ofan aromatic vinyl compound in the presence of 20-70 parts by weight,preferably 30-60 parts by weight, of a conjugated diene-based syntheticrubber with

(B) a vinyl cyanide compound/aromatic vinyl compound copolymer in whichthe content of the vinyl cyanide compound is in the range of 50-75% byweight, preferably 50-66% by weight, and the content of the aromaticvinyl compound is thus in the range of 25-50% by weight, preferably34-50% by weight, so that the rubber content in the blend is in therange of 10-20% by weight, preferably 13-18% by weight (theaforementioned parts by weight and % by weight are respectively thevalues based on the total amount of these components in question as100). Preferably, the composition is one which has the content of thevinyl cyanide compound in the vinyl cyanide compound/aromatic vinylcompound copolymer contained therein in the range of 50-75% by weight,particularly 50-65% by weight.

(ii) The graft copolymer satisfies the following equations:

0.30≦(G-R)/R≦0.50, preferably

0.37≦(G-R)/R≦0.50

wherein

G: a percentage by weight of a gel in the graft copolymer, calculated onthe insoluble matter obtained by dissolution of the graft copolymer inacetonitrile and then separation from the solution by centrifugation.

R: a rubber content of the graft copolymer.

(iii) The graft copolymer has a specific viscosity in the range of0.04-0.09, preferably 0.058-0.085 determined on a solution of 0.1 g ofan acetonitrile soluble portion of the graft copolymer in 100 ml ofdimethylformamide measured by a viscometer. As described above, both ofthe vinyl cyanide compound/aromatic vinyl compound copolymer to beincorporated in the graft copolymer and the high nitrile thermoplasticresin composition after the incorporation of the copolymer have aspecific viscosity in the range of 0.04-0.09, preferably 0.058-0.085.

(iv) The graft copolymer is produced by emulsion polymerization ofpredetermined amounts of the monomers in the conjugated diene-basedsynthetic rubber latex having an average diameter of rubber particles inthe range of 0.01-10 μm, preferably 0.1-0.5 μm.

EXPERIMENTAL EXAMPLES

The following Examples and Comparative Examples are provided forspecifically illustrating the present invention. The properties of theinternal box of a refrigerator were evaluated for the following 5 items.

(1) Flexural modulus

Flexural modulus was measured in accordance with JIS K-7203 and taken asan index of rigidity required for the internal box of a refrigerator.

(2) Izod impact value

Izod impact value was measured in accordance with JIS K-7110 and takenas an index of impact resistance required for the internal box of arefrigerator.

(3) Melt flow rate

Melt flow rate was measured in accordance with JIS K-7210 and taken asan index of formability required for the internal box of a refrigerator(test condition: Table 1, condition No. 11) (g/10 min).

(4) Critical distortion value

A test piece in the shape of strip of 35 mm×230 mm×2 mm prepared bycompression molding was set on a bending form (a bending distortion jigsimilar to a 1/4 elliptical jig having a maximum distortion value of0.7%), which was left standing at a temperature of 23° C. under anatmosphere of CFC-11, HCFC-123 or HCFC-141b. The appearance of the testpiece was then visually judged. The test results were taken as theindices of stress cracking resistance against CFC-11, HCFC-123 andHCFC-141b.

(5) Low temperature distortion value for generating whitening

A test piece was prepared such that a rigid polyurethane foam producedin accordance with the in-situ foaming method by means of CFC-11,HCFC-123 or HCFC-141b was in adherence to a dumbbell test piece of theresin composition prepared by compression forming. The test piece wasfixed on a jig in such a state that tensile distortion was loaded to thetest piece at 23° C., and was cooled to -20° C., whereby the presence ofcrazing or cracking after 17 hours was visually judged. The judgementswere taken as indices of stress cracking resistance against CFC-11,HCFC-123 and HCFC-141b.

Dumbbell test piece had a larger width of 30 mm, a smaller width of 10mm, a length of 115 mm and a thickness of 1 mm, and a polyurethane foamhaving a width of 10 mm, a thickness of 10 mm and a length of 50 mm wasadhered to the smaller width portion.

(6) Measurement of AN content

The solvent*-soluble portion of the graft copolymer after having beenisolated and dried and an AN/ST (acrylonitrile/styrene) copolymer assuch were subjected to elemental analysis to obtain the "content of theacrylonitrile component (% by weight)" from the ratios of C, H and N.

(7) Specific viscosity

The 0.1 g portion of the solvent*-soluble portion of the graft copolymerafter having been isolated and dried and an AN/ST copolymer as such weretaken and dissolved in 100 ml of dimethylformamide, and the specificviscosity was measured at 23° C. by a viscometer.

(8) Degree of grafting

The graft copolymer was dispersed in a solvent* and separated into asolvent-soluble portion and solvent-insoluble portion with a centrifuge.The weight fraction of the solvent soluble portion (having been dried)was expressed as G and the rubber content of the graft copolymer wasexpressed as R to calculate the degree of grafting by an equation(G-R)/R.

(9) Average rubber particle diameter

The average rubber particle diameter (μm) of a graft copolymer latex wasmeasured with a Coulter Nano-Sizer.

EXAMPLE 1 A. Preparation of a vinyl cyanide compound/aromatic vinylcompound/diene-based rubber graft copolymer (A)

(a) Preparation of a diene-based rubber latex

    ______________________________________    1,3-butadiene      90     parts by weight    Styrene            10     parts by weight    Fatty acid soap    4      parts by weight    Potassium persulfate                       0.15   parts by weight    t-dodecylmercaptan 0.3    parts by weight    Deionized water    155    parts by weight    ______________________________________

The mixture comprising the above-described components was charged in astainless steel reaction vessel, and reaction was continued withagitation under a nitrogen stream at 68° C. for 6 hours. The temperatureof the mixture was then raised from 68° C. to 80° C. over 1.5 hours. Thereaction was further continued at 80° C. for 2.5 hours and completed bycooling the mixture.

The latex obtained had a solid content of 39.9%.

(b) Preparation of a graft copolymer

    ______________________________________    Diene-based rubber latex                     50      parts by weight    described in (a)         (as the solid content)    Sodium alkyldiphenyl ether                     2       parts by weight    disulfonate              (as the solid content)    Deionized water  200     parts by weight                             (as the solid content)    Potassium persulfate                     0.085   parts by weight                             (as the solid content)    ______________________________________

The above-mentioned components were charged in a flask and kept at 65°C. with agitation under a nitrogen stream, and the first stage monomermixture described below was successively added over a period of 4 hours.

    ______________________________________    Acrylonitrile      27.5   parts by weight    Styrene            19.2   parts by weight    n-dodecylmercaptan 1.15   parts by weight    ______________________________________

After the addition of the first stage monomer mixture, the reactionsystem was kept at a temperature of 65° C., and the second stage monomerdescribed below was added continuously over a period of 1 hour.

    ______________________________________    Styrene     3.3 parts by weight    ______________________________________

In addition, on 30 minutes after starting the addition of the firststage monomer mixture, the following initiator was continuously added asa solution in deionized water over a period of 4 hours.

    ______________________________________    Potassium persulfate                    0.17 part by weight    ______________________________________

The resin latex obtained had a solid content of 3.5%.

The resin latex was coagulated with an aqueous magnesium sulfatesolution, washed with water, dried to give a polymer powder.

B. Preparation of a vinyl cyanide compound/aromatic vinyl compoundcopolymer (B)

    ______________________________________    Acrylonitrile       55     parts by weight    Styrene             5      parts by weight    Terpene oil         0.52   parts by weight    Di-t-butylparacresol                        0.04   parts by weight    Deionized water     90     parts by weight    Acrylic acid-octyl acrylate                        0.03   parts by weight    copolymer    Sodium chloride     0.18   parts by weight    ______________________________________

The mixture comprising the above-described components was charged in astainless steel reaction vessel. The temperature of the mixture wasraised to 105° C. with agitation under a nitrogen atmosphere, and 0.15part by weight of 1-t-butylazo-1-cyano-cyclohexane dissolved in a smallamount of styrene was added with pressure by nitrogen to startpolymerization reaction. Immediately after the initiation, 40 parts byweight of styrene was continuously added to the reaction system over aperiod of 4 hours. During this period, the reaction temperature wasraised from 105° C. on the initiation of the polymerization to 141° C.After the continuous addition of styrene to the reaction system hadcompleted, the temperature was raised to 145° C. over a period of 20minutes, and stripping was conducted at this temperature for 2.5 hours.Then, according to the usual manner, the reaction system was cooled andthe polymer was separated, washed and dried to give a polymer in theshape of beads.

Twenty-eight parts by weight of the vinyl cyanide compound/aromaticvinyl compound/conjugated diene-based synthetic rubber graft copolymer(A) obtained by the above-described method and 72 parts by weight of thevinyl cyanide compound/aromatic vinyl compound copolymer (B) weremelt-kneaded to give a high nitrile thermoplastic resin compositionhaving a rubber content of 14% by weight.

EXAMPLE 2

Thirty-two parts by weight of the vinyl cyanide compound/aromatic vinylcompound/conjugated diene-based synthetic rubber graft copolymer (A) and68 parts by weight of the vinyl cyanide compound/aromatic vinyl compoundcopolymer (B) referred to in Example 1 were melt-kneaded on a Banburymixer to give a high nitrile content thermoplastic resin compositionhaving a rubber of 16% by weight.

EXAMPLE 3

Thirty-six parts by weight of the vinyl cyanide compound/aromatic vinylcompound/conjugated diene-based synthetic rubber graft copolymer (A) and64 parts by weight of the vinyl cyanide compound/aromatic vinyl compoundcopolymer (B) referred to in Example 1 were melt-kneaded on a Banburymixer to give a high nitrile content thermoplastic resin compositionhaving a rubber of 18% by weight.

EXAMPLE 4

Twenty-eight parts by weight of the vinyl cyanide compound/aromaticvinyl compound/conjugated diene-based synthetic rubber graft copolymer(A) obtained in the same manner as in the part A of Example 1 exceptthat, in the preparation of the graft copolymer of the part A (b) inExample 1, the composition of the first stage monomer mixture waschanged into the following composition:

    ______________________________________    Acrylonitrile      27.5   parts by weight    Styrene            19.2   parts by weight    n-Dodecylmercaptan 4.6    parts by weight    ______________________________________

and 72 parts by weight of the vinyl cyanide to in Example 1 weremelt-kneaded on a Banbury mixer to give a high nitrile contentthermoplastic resin composition having a rubber content of 14% byweight.

EXAMPLE 5

Twenty-eight parts by weight of the vinyl cyanide compound/aromaticvinyl compound/conjugated diene-based synthetic rubber graft copolymer(A) obtained in the same manner as in the part A of Example 1 exceptthat, in the preparation of the graft copolymer of the part A (a) ofExample 1, the composition:

    ______________________________________    Diene-based rubber latex                        50     parts by weight    of A (a) of Example 1      (solid content)    Sodium alkyldiphenyl ether                        2.5    parts by weight    disulfonate                (solid content)    Deionized water     200    parts by weight                               (solid content)    Potassium persulfate                        0.085  parts by weight                               (solid content)    ______________________________________

was initially charged into a flask and that the first stage monomermixture having the following composition:

    ______________________________________    Acrylonitrile   27.5 parts by weight    Styrene         19.2 parts by weight    n-Dodecyl mercaptan                     2.3 parts by weight    ______________________________________

was used, and 72 parts by weight of the vinyl cyanide compound/aromaticvinyl compound copolymer (B) obtained in the same manner as in the partB of Example 1 except that, in the preparation of the vinyl cyanidecompound/aromatic vinyl compound copolymer, the composition:

    ______________________________________    Acrylonitrile       55     parts by weight    Styrene             5      parts by weight    Terpene oil         0.65   parts by weight    Di-t-butyl-para-cresol                        0.02   parts by weight    Deionized water     70     parts by weight    Acrylic acid-octyl acrylate                        0.03   parts by weight    copolymer    Sodium chloride     0.18   parts by weight    ______________________________________

was charged, were melt-kneaded on a Banbury mixer to give a high nitrilecontent thermoplastic resin composition having a rubber content of 14%by weight.

EXAMPLE 6

Twenty-eight parts by weight of the vinyl cyanide compound/aromaticvinyl compound/conjugated diene-based synthetic rubber graft copolymer(A) obtained in the same manner as in the part A of Example 1 exceptthat, in the preparation of the graft copolymer of the part A (b) ofExample 1, the first stage monomer mixture had the followingcomposition:

    ______________________________________    Acrylonitrile      35     parts by weight    Styrene            11.7   parts by weight    n-Dodecyl mercaptan                       2.3    parts by weight    ______________________________________

and 72 parts by weight of the vinyl cyanide compound/aromatic vinylcompound copolymer (B) obtained in the same manner as in the part B ofExample 1 except that, in the preparation of the vinyl cyanidecompound/aromatic vinyl compound copolymer, the composition:

    ______________________________________    Acrylonitrile       70     parts by weight    Styrene             3      parts by weight    Terpene oil         0.6    parts by weight    Di-t-butyl-para-cresol                        0.02   parts by weight    Deionized water     70     parts by weight    Acrylic acid-octyl acrylate                        0.03   parts by weight    copolymer    Sodium chloride     0.4    parts by weight    ______________________________________

was used and the amount of styrene to be added continuously was 27 partsby weight, were melt-kneaded on a Banbury mixer to give a high nitrilecontent thermoplastic resin composition having a rubber content of 14%by weight.

COMPARATIVE EXAMPLE 1

Twenty-eight parts by weight of the vinyl cyanide compound/aromaticvinyl compound/conjugated diene-based synthetic rubber graft copolymer(A) obtained in the same manner as in the part A of Example 1 exceptthat, in the preparation of the graft copolymer of the part A (b) ofExample 1, the temperature of the graft copolymerization was set at 62°C. and the first stage monomer mixture had the following formulation:

    ______________________________________    Acrylonitrile   27.5 parts by weight    Styrene         19.2 parts by weight    n-Dodecyl mercaptan                     6.9 parts by weight    ______________________________________

and 72 parts by weight of the vinyl cyanide compound/aromatic vinylcompound copolymer (B) referred to in the part B of Example 1 weremelt-kneaded on a Banbury mixer to give a high nitrile contentthermoplastic resin composition having a rubber content of 14% byweight.

COMPARATIVE EXAMPLE 2

    ______________________________________    Diene-based rubber latex of the                        35     parts by weight    part A (a) of Example 1    Fatty acid soap     0.63   parts by weight    Potassium hydroxide 0.06   parts by weight    ______________________________________

These components were charged into a flask and maintained at atemperature of 72° C. with agitation under nitrogen stream, and thefollowing components were continuously added over a period of 4.5 hours:

    ______________________________________    Acrylonitrile      29.2   parts by weight    Styrene            35.8   parts by weight    Terpene oil        0.33   parts by weight    Potassium persulfate                       0.33   parts by weight    ______________________________________

The resin latex thus obtained had a solid content of 39.7%

The resin latex was coagulated in an aqueous magnesium sulfate solution,the coagulum obtained was washed with water and dried to give the vinylcyanide compound/aromatic vinyl compound/conjugated diene-based rubbergraft copolymer (A).

A vinyl cyanide compound/aromatic vinyl compound copolymer (B) wasobtained in the same manner as in the part B of Example 1 except that,in the preparation of the vinyl cyanide compound/aromatic vinyl compoundcopolymer, the composition:

    ______________________________________    Acrylonitrile       45     parts by weight    Styrene             11.4   parts by weight    Terpene oil         0.45   parts by weight    Di-t-butyl-para-cresol                        0.04   parts by weight    Deionized water     70     parts by weight    Acrylic acid-octyl acrylate                        0.03   parts by weight    copolymer    Sodium chloride     0.18   parts by weight    ______________________________________

was used and the amount of styrene to be added continuously was 43.6parts by weight. Forty parts by weight of the vinyl cyanidecompound/aromatic vinyl compound/diene-based synthetic rubber graftcopolymer (A) and 60 parts by weight of the vinyl cyanidecompound/aromatic vinyl compound copolymer (B) obtained by theabove-described methods were melt-kneaded on a Banbury mixer to give ahigh nitrile thermoplastic resin composition having a rubber content of14% by weight.

COMPARATIVE EXAMPLE 3

"TUFREX YT-212" manufactured by Mitsubishi Monsanto Chemical Company,Japan was prepared. This is an ABS resin which has widely been used forinternal boxes of refrigerators.

    __________________________________________________________________________                  Example 1                        Example 2                              Example 3                                    Example 4                                          Example 5                                                Example 6    __________________________________________________________________________    AN content of graft                  52    52    52    55    54    66    copolymer (% by weight)    Specific viscosity of                  0.081 0.081 0.081 0.040 0.060 0.070    graft copolymer    Degree of grafting of                  0.47  0.47  0.47  0.33  0.37  0.48    graft copolymer    AN content of AN/ST                  57    57    57    57    55    66    copolymer (% by weight)    Specific viscosity of                  0.072 0.072 0.072 0.072 0.058 0.066    AN/ST copolymer    Rubber content in high                  14    16    18    14    14    14    nitrile thermoplastic    resin (% by weight)    Rubber particle diameter                  0.15  0.16  0.15  0.15  0.10  0.10    of graft copolymer (μm)    Flexural modulus (kg/cm.sup.2)                  28000 26000 24000 27500 27000 28000    Izod impact value                  30    42    52    32    25    25    (kg · cm/cm)    Melt flow rate (g/10                  3.0   2.5   2.0   4.0   6.0   4.0    min.)    Critical distortion    value:    CFC-11        ◯                        ◯                              ◯                                    ◯                                          ◯                                                ◯                  No change                        No change                              No change                                    No change                                          No change                                                No change    HCFC-123      ◯                        ◯                              ◯                                    ◯                                          ◯                                                ◯                  No change                        No change                              No change                                    No change                                          No change                                                No change    HCFC-141b     ◯                        ◯                              ◯                                    ◯                                          ◯                                                ◯                  No change                        No change                              No change                                    No change                                          No change                                                No change    Low temperature    distortion value for    generating whitening:    CFC-11        1.3   1.3   1.3   1.3   1.3   1.3    HCFC-123      0.8   0.8   0.8   0.8   0.8   0.9    HCFC-141b     0.8   0.8   0.8   0.8   0.8   0.9    __________________________________________________________________________                                 Comparative                                        Comparative                                               Comparative                                 Example 1                                        Example 2                                               Example 3    __________________________________________________________________________                   AN content of graft                                 55     43     23                   copolymer (% by weight)                   Specific viscosity of                                 0.026  0.093  0.065                   graft copolymer                   Degree of grafting of                                 0.21   0.85   0.49                   graft copolymer                   AN content of AN/ST                                 57     47     26                   copolymer (% by weight)                   Specific viscosity of                                 0.072  0.069  0.100                   AN/ST copolymer                   Rubber content in high                                 14     14     13                   nitrile thermoplastic                   resin (% by weight)                   Rubber particle diameter                                 0.15   0.21   0.40                   of graft copolymer (μm)                   Flexural modulus (kg/cm.sup.2)                                 27500  26000  24000                   Izod impact value                                 10     28     20                   (kg · cm/cm)                   Melt flow rate (g/10                                 5.0    3.0    4.5                   min.)                   Critical distortion                   value:                   CFC-11        ◯                                        ◯                                               ◯                                 No change                                        No change                                               No change                   HCFC-123      ◯                                        ×                                               ×                                 No change                                        Crazing at                                               Whole                                        0.4%   swelling                   HCFC-141b     ◯                                        ×                                               ×                                 No change                                        Crazing at                                               Whole                                        0.5%   swelling                   Low temperature                   distortion value for                   generating whitening:                   CFC-11        1.3    1.1    0.6                   HCFC-123      0.8    0.4    0.2                   HCFC-141b     0.8    0.2    0.2    __________________________________________________________________________

Analysis and evaluation of the results

(1) As is apparent from Examples and Comparative Examples, stresscracking resistances against CFC-11, HCFC-123 and in HCFC-141b depend onthe ratios of the vinyl cyanide compound/aromatic vinyl compound in thegraft copolymer and in the vinyl cyanide compound/aromatic vinylcompound copolymer.

When the content of the vinyl cyanide compound is in the range of 50-75%by weight, stress cracking is not found on the measurement of thecritical distortion values in the atmospheres of HCFC-123 and HCFC-141b.When the content of the vinyl cyanide compound is less than 50% byweight, stress cracking is found at the distortion of 0.4% (HCFC-123) or0.5% (HCFC-141b), and the ABS resin is swollen and dissolved.

When the content of the vinyl cyanide compound is in the range of 50-75%by weight, the low temperature distortion value for generating whiteningis 1.3% or more in the case where a rigid polyurethane foam foamed withCFC-11 is in adherence and 0.8% or more in the case where a rigidpolyurethane foam foamed with HCFC-123 or HCFC-141b is in adherence. Allof these values exceed the value of 0.6% in the case where a rigidpolyurethane foam foamed with CFC-11 is in adherence to an ABS resin asa model of a current refrigerator and are thus improved. When thecontent of the vinyl cyanide compound is less than 50% by weight, thelow temperature distortion value for generating whitening is 0.4% and0.2% in the cases where rigid polyurethane foams foamed with HCFC-123and HCFC-141b are respectively in adherence, and 0.2% in the case wherea rigid polyurethane foam foamed with HCFC-123 is in adherence to an ABSresin. All of these values are inferior to the value of the currentrefrigerator model.

From these results, it is assumed that an internal box of a refrigeratormanufactured by a high nitrile content thermoplastic resin compositionhaving a ratio of a vinyl cyanide compound/aromatic vinyl compound suchthat the amount of the vinyl cyanide compound comprises 50-75% by weighthas high stress cracking resistance against CFC-11, HCFC-123 andHCFC-141b.

(2) As is apparent from Examples and Comparative Examples, the highbalance of rigidity and impact resistance of a high nitrilethermoplastic resin composition depends on the degree of grafting agraft copolymer.

When the degree of grafting is in the range of 0.30-0.50, the Izodimpact value is 25 kg.cm/cm or more with a rubber content of 14% byweight and a flexural modulus of 27000 kg/cm² or more. When the degreeof grafting is less than 0.30, the Izod impact value is only 10 kg.cm/cmeven with the rubber content of 14% by weight.

From these results, it is assumed that an internal box of a refrigeratormanufactured by a high nitrile content thermoplastic resin compositionwith a degree of grafting in the range of 0.30-0.50 has high balance ofrigidity and impact resistance.

(3) It is thought, in view of ABS resins currently used for the internalbox and door interior of a refrigerator, that a flexural modulus of23000 kg/cm² or more is required for preventing the deformation of thebox vacuum-formed, and an Izod impact value of 15 kg.cm/cm or more isrequired for avoiding the cracking which may be produced when an articlehoused in the refrigerator hits on the internal box. As is seen fromExamples, the high nitrile thermoplastic resin composition having arubber content in the range of 10-20% by weight meets the requirements.

(4) It is regarded as being adequate that the melt flow rate (conditionNo. 11) for conventional methods for producing the internal box of arefrigerator such as sheet extrusion and vacuum forming is in the rangeof 1.0-8.0 g/10 min. When the melt flow rate is less than 1.0 g/10 min,the sheet extrusion or vacuum forming is carried out at highertemperatures which approach the decomposition temperature of the resincomposition. On the other hand, when it exceeds 8.0 g/10 min, the resinsheet formed sags due to its weight upon the sheet forming whereby itbecomes difficult to conduct the sheet forming or the quality of theproduct is lowered due to unevenness in the thickness of the sheet. Asis shown in Examples, the melt flow rate (condition No. 11) depends onthe factors such as ratio of vinyl cyanide compound/aromatic vinylcompound, degree of grafting rubber content, specific viscosity and thelike. When these factors are within the ranges defined according to thepresent invention, the melt flow rate is generally in the range of1.0-8.0 g/10 min.

INDUSTRIAL APPLICABILITY

The resin composition according to the present invention isfluorinated/chlorinated hydrocarbon resistant, and thus the internal boxof a refrigerator made from it also has a high resistance to thesolvent/foaming agent. Therefore, the resin composition according to thepresent invention is advantageously used at present or in future underthe situation of severer restriction of use of fluorinated/chlorinatedhydrocarbon solvents/foaming agents.

We claim:
 1. A high nitrile thermoplastic resin composition,characterized by the following conditions (i)-(vii):(i) the high nitrilethermoplastic resin composition comprises a blend of: (A) a graftcopolymer obtained by polymerizing, in the presence of 20 to 70 parts byweight of a conjugated diene-based synthetic rubber, 30 to 80 parts byweight of a monomer mixture consisting essentially of 50 to 75% byweight of a vinyl cyanide compound and 25 to 50% by weight of anaromatic vinyl compound, with (B) a vinyl cyanide compound/aromaticvinyl compound copolymer in which the content of the vinyl cyanidecompound is in the range of 50 to 75% by weight and the content of thearomatic vinyl compound is thus in the range of 25 to 505 by weight suchthat the rubber content is in the range of 10 to 20% by weight, theparts by weight and % by weight being respectively the values based onthe total amount of these components in question as 100; (ii) the graftcopolymer (A) satisfies the following equation:

    0.30≦(G-R)/R≦0.50,

wherein G means a percentage by weight of a gel in the graft copolymer,calculated in the insoluble matter obtained by dissolution of the graftcopolymer in acetonitrile and then separation from the solution bycentrifugation, and R means a rubber content of the graft copolymer;(iii) the graft copolymer (A) has a specific viscosity in the range of0.04-0.09 determined on a solution of 0.1 g of an acetonitrile-solubleportion of the graft copolymer in 100 ml of dimethylformamide measuredby a viscometer; (iv) the graft copolymer (A) has been produced byemulsion polymerization of predetermined amounts of the monomers in theconjugated diene-based synthetic rubber latex having an average diameterof rubber particles in the range of 0.01-10 μm; (v) the high nitrilethermoplastic resin composition has a content of the vinyl cyanidecompound in the vinyl cyanide compound/aromatic vinyl compound copolymercontained therein in the range of 50-75% by weight; (vi) the vinylcyanide compound/aromatic vinyl compound copolymer (B) has a specificviscosity in the range of 0.04-0.09; and (vii) the high nitrilethermoplastic resin composition has a specific viscosity in the range of0.04-0.09.
 2. The high nitrile thermoplastic resin composition accordingto claim 1, whereinthe graft copolymer (A) is obtained by polymerizing,in the presence of 30 to 60 parts by weight of a conjugated diene-basedsynthetic rubber, 40 to 70 parts by weight of a monomer mixtureconsisting essentially of 50 to 66% by weight of a vinyl cyanidecompound and 34 to 50% by weight of an aromatic vinyl compound, thevinyl cyanide compound/aromatic vinyl compound copolymer (B) has acontent of the vinyl cyanide compound in the range of 50 to 66% byweight, and the content of the aromatic vinyl compound is thus in therange of 34 to 50% by weight such that the rubber content is in therange of 13 to 18% by weight, the parts by weight and % by weight beingrespectively the values based on the total amount of these components inquestion as 100, the graft copolymer (A) satisfies the followingequation:

    0.37≦(G-R)/R≦0.50,

wherein G and R are as defined in claim 5, the graft copolymer (A) has aspecific viscosity in the range of 0.058-0.085, the conjugateddiene-based synthetic rubber latex has an average diameter of rubberparticles in the range of 0.1-0.5 μm, the content of the vinyl cyanidecompound in the vinyl cyanide compound/aromatic vinyl compound copolymeris in the range of 50 to 66% by weight, the vinyl cyanidecompound/aromatic vinyl compound copolymer (B) and the high nitrilethermoplastic resin composition each has a specific viscosity in therange of 0.058-0.085.